In electrical power distribution systems, several needs compete and must be simultaneously considered in managing electrical power distribution. A first concern has to do with maintaining delivered electrical power voltage levels within predetermined limits. A second concern relates to overall efficiency of electrical power generation and distribution. A third concern relates to these and other concerns in light of changing electrical loading of the system and variations in the character of the loading. A fourth concern relates to power system management under conditions associated with an increased probability of compromise of large scale ability to deliver appropriate power.
It is generally desirable to manage a power grid to reduce overall power consumption while maintaining adequate delivered voltage minimum and maximum levels across the system. In other words, the voltage levels actually delivered to various users need to be kept within predetermined limits while delivering power efficiently, without undue power loss in the delivery system or power grid, including the power generation equipment. As power usage within the system changes, in accordance with diurnal, weekly and seasonal factors, among others, need for regulation of power distribution changes as well. To an extent, some of these changes are reasonably predictable, however, other aspects of these changes may not be readily predictable.
Predictable changes in system loading are forecast by integrating power demand over time and considering this draw together with other factors, such as increased outdoor temperature and known diurnal variation patterns. For example, when summer heat results in increased power demand for air conditioning during the course of the day, fast food power demand associated with the end of the work day may indicate that a power shortage is imminent. Typically, measurements of power demand and delivered voltage are made every few seconds, filtered to reveal variations with periodicities on the order of a few minutes or longer, and adjustments to voltage are made perhaps once or twice an hour. This is called “automated conservation voltage reduction” and is intended to reduce overall energy demand.
However, compromise of power delivery capability due, for example, to extreme weather conditions (e.g., gale winds affecting the distribution system) or unforeseen decrease in available power (e.g., generator malfunction) is not necessarily amenable to precise forecasting but is observable. As a result, there is need for dynamic system adjustment in response to observed changes in system capacity, conditions and loading.
Increased probability of compromise of large scale ability to deliver appropriate power may include increased probability of system-wide failure or blackout of an area, where “system-wide failure” could mean either a large grid being shut down or a smaller grid being isolated from a larger grid, with a potential result that the smaller grid then would be shut down or malfunction. In some cases, grid failure may be caused by automated shutdown of one or more generators in response to determination of grid conditions ill-suited to the generator in order to obviate catastrophic generator failure.
The conditions associated with an increased probability of compromise of large scale ability to deliver appropriate power are varied, and can range from “brownout” situations to complete disruption of electrical service or “blackouts”. Some types of power consumption relate to relatively vital concerns, such as hospitals, infrastructural support systems (telephone, police, fire protection, electrical traffic signals and the like) and others relate to more quotidian concerns, such as air conditioning, fast food operations and industrial operations such as aluminum smelters and the like, as equipment is added to or removed from service, for example.
The latter types of concerns can present a high electrical draw at certain times of day. However, interruption of power delivery to such operations does not usually present life-threatening consequences when such operations are without electrical power.
Further, in the event of severe disruption or demand, grid systems used for delivery of electrical power can experience catastrophic failure when load conditions presented to generators in the system are such that one or more electrical generators are automatically shut down or disconnected from the system. This situation obviously places increased demand or even less suitable loading conditions on other generators or grids to which the grid is coupled. As a result, other generators or grids coupled to the affected grid may disconnect from the affected grid, potentially resulting in a blackout. Such blackouts can be extremely widespread in electrical generation and distribution systems employed multiple coupled grids each having electrical generation capability.
Prior art power regulation systems include fusing, opening switches at a power station or substation to remove load components, or sending out trucks with technicians to manually open switches to remove portions of the load from the system, or to manually adjust power regulators and set points. These methods are not amenable to rapid, dynamic load adjustment or rapid, dynamic power management.
Another prior art system provides equipment at the user site that disables high load appliances, such as hot water heaters, on demand. This may be based on forecasting of anticipated excess demand. Such systems are known as “demand side control” systems. These tend to be expensive, in part because the number of control switches is high.
Needed are systems, apparatus and processes for (i) optimizing efficiency of power delivery while maintaining delivered voltage levels within acceptable limits under changing conditions for electrical power demand and (ii) coping with conditions associated with an increased probability of compromise of large scale ability to deliver appropriate power in such a way as to avoid compromise of critical concerns and to further avoid catastrophic electrical system failure.